Enzima conversora de angiotensina no líquido pericárdico: estudo comparativo com a atividade sérica / Angiotensin-converting enzyme in pericardial fluid: comparative study with serum activity

FUNDAMENTO: A caracterização de uma enzima conversora de angiotensina (ECA) no líquido pericárdico humano é relevante diante do seu papel na liberação de angiotensina II e, portanto, do papel do pericárdio na homeostase cardivascular. OBJETIVO: Isolar e caracterizar uma ECA do líquido pericárdico humano. Comparar as atividades conversoras de angiotensina I do fluido pericárdico e do soro de pacientes submetidos à cirurgia cardiovascular. MÉTODOS: A enzima do líquido pericárdico humano foi purificada por meio de etapas cromatográficas e caracterizada por eletroforese em gel de poliacrilamida (SDS-PAGE), hidrólise de angiotensina I, bradicinina, Hip-His-Leu e substratos sintéticos com supressão interna de fluorescência. Lisinopril foi usado como inibidor. A atividade de ECA foi determinada em amostras de sangue e líquido pericárdico de 23 pacientes submetidos à cirurgia cardiovascular. RESULTADOS: A ECA purificada (MM = 140 kDa) libera angiotensina II, hidrolisa a bradicinina e o substrato Hip-His-Leu. Os parâmetros cinéticos k cat,(s-1) e k cat/Km (µM-1. s-1) foram respectivamente: Hip-His-Leu (1,14 e 7 x 10 -4), Abz-YRK(Dnp)P-OH (2,60 e 0,77), Abz-LFK(Dnp)-OH (2,77 e 0,36) e Abz-SDK(Dnp)P-OH (1,92 e 0,19). As atividades conversoras de angiotensina I (média ± DP) do líquido pericárdico e no soro foram, respectivamente, 3,16 ± 0,90 mU x mg -1x min-1 e 0,33 ± 0,11 mU x mg -1x min-1 . A diferença foi significativa entre os dois fluidos. CONCLUSÃO: Uma ECA com grande similaridade com a enzima somática foi isolada do fluido pericárdico humano. A atividade conversora de angiotensina I é maior no líquido pericárdico quando comparada com a atividade do soro. Esses dados constituem importante evidência do papel do líquido pericárdico no metabolismo de peptídeos ativos.

BACKGROUND: The characterization of an angiotensin-converting enzyme (ACE) in human pericardial fluid is relevant, considering its role in the angiotensin II release and thus, the role of the pericardium in cardiovascular homeostasis. OBJECTIVE: To isolate and characterize an ACE from human pericardial fluid and to compare the angiotensin I converting activities of the pericardial fluid with that of the serum in patients submitted to cardiovascular surgery. METHODS: The enzyme from human pericardial fluid was purified through chromatographic steps and characterized by polyacrylamide gel electrophoresis (SDS-PAGE), hydrolysis of angiotensin I, bradykinin, Hip-His-Leu and synthetic substrates with internal fluorescence suppression. Lisinopril was used as inhibitor. The ACE activity was measured in blood and pericardial fluid samples of 23 patients submitted to cardiovascular surgery. RESULTS: The purified ACE (MM = 140 kDa), releases angiotensin II, hydrolyses bradykinin and the Hip-His-Leu substrate. The kinetic parameters k cat,(s-1) and k cat/Km (µM-1. s-1) were, respectively: Hip-His-Leu (1.14 and 7 x 10 -4) ; Abz-YRK(Dnp)P-OH (2.60 and 0.77), Abz-LFK(Dnp)-OH (2.77 and 0.36) and Abz-SDK(Dnp)P-OH (1.92 and 0.19). The angiotensin I converting activities (mean ± SD) in the pericardial fluid and in blood, were, respectively: 3.16 ± 0.90 mU x mg -1x min-1 and 0.33 ± 0.11 mU x mg -1x min-1. The difference was significant between the two fluids. CONCLUSION: An ACE that bears great similarity with the somatic enzyme was isolated from human pericardial fluid. The angiotensin I converting activity is higher in the pericardial fluid when compared to the serum activity. These data are important evidence of the role of the pericardial fluid in the metabolism of active peptides.

Correlações entre o teor de colágeno no miocárdio ventricular esquerdo humano medido através de métodos / Correlations between the collagen content of the human left ventricular myocardium, measured by biochemical and morphometric methods

OBJECTIVE: To assess, in myocardium specimens obtained from necropsies, the correlation between the concentration of hydroxyproline, measured with the photocolorimetric method, and the intensity of fibrosis, determined with the morphometric method. METHODS: Left ventricle myocardium samples were obtained from 45 patients who had undergone necropsy, some of them with a variety of cardiopathies and others without any heart disease. The concentrations of hydroxyproline were determined with the photocolorimetric method. In the histologic sections from each heart, the myocardial fibrosis was quantified by using a light microscope with an integrating ocular lens. RESULTS: A median of, respectively, 4.5 and 4.3 mug of hydroxyproline/mg of dry weight was found in fixed and nonfixed left ventricle myocardium fragments. A positive correlation occurred between the hydroxyproline concentrations and the intensity of fibrosis, both in the fixed (Sr=+0.25; p=0.099) and in the nonfixed (Sr=+0.32; p=0.03) specimens. CONCLUSION: The biochemical methodology was proven to be adequate, and manual morphometry was shown to have limitations that may interfere with the statistical significance of correlations for the estimate of fibrosis intensity in the human myocardium